In general, a double-sided printed circuit board is based on a CCL (copper clad laminate) having copper (cu) foils laminated on both sides of an insulation member. To create electrical paths in both copper foils, holes are formed using a drill, and copper electroplating is performed to connect both copper foils by a plating layer. Then, a UV sensitive dry film is applied for circuit formation, followed by UV radiation for selective patterning. Thereafter, circuit patterns are formed on both copper foils by etching, and PSR (Photoimagable Solder Resist) is applied thereto for insulation. Surface treatment such as gold plating is performed on the surface where final parts are mounted, thereby manufacturing the double-sided printed circuit board.
A multilayer printed circuit board can be also manufactured in the same way as the double-sided printed circuit board, until the step of circuit formation. After circuit formation, a prepreg and a copper foil are laminated on the top and bottom instead of applying PSR thereon, followed by heating and pressing. Thus, the multilayer printed circuit board means a build-up board including a plurality of PCB. In the multilayer printed circuit board, via-holes can be formed by a laser process for electrical connection between internal and external circuit patterns, and the inner surface of the via-hole is plated to manufacture the printed circuit board. Thereafter, if necessary, a solder-resist layer can be further formed as a protecting layer on the plating layer, or additional external layers can be formed.
Meanwhile, the copper clad laminate can be produced using a prepreg that is a raw material for the printed circuit board for the semiconductor package. In addition, the conventional prepreg and copper clad laminate used in the printed circuit board for the semiconductor package are basically required to have physical properties of high heat resistance, high rigidity, and low coefficient of thermal expansion (Low CTE), and thus a larger amount of inorganic filler relative to a resin has been used.
In this regard, when the inorganic filler is used in an excessive amount of 50% or more relative to the total weight, separation between the resin and the inorganic filler occurs during a high-temperature and high-pressure lamination process, and thus a substrate may have a non-uniform insulation layer. That is, when the BT resin and epoxy resin are conventionally used, the curing occurs at around 200° C. Thus, during heating and pressing of the prepreg laminated on the metal foil, flowability of the resin and inorganic filler becomes poor, resulting in separation therebetween. Such separation may cause a deterioration of physical properties of the substrate, and in particular, it negatively affects heat resistance and reliability.
However, thermosetting resin compositions capable of preventing separation of the resin and the inorganic filler while having excellent heat resistance, and methods for providing a metal clad laminate for a printed circuit board using the same have not been developed yet.
During the manufacturing process of the multilayer printed circuit board, a prepreg for the multilayer and a copper foil are laminated, and then the external copper foil is processed in the same manner as in the internal circuit formation, and PSR is applied to manufacture a 4-layer printed circuit board. However, as the prepreg for copper clad laminate (CCL) that is produced by direct pressing in a CCL maker and the prepreg for the multilayer that fills the internal circuit patterns by pressing in a PCB maker are compared to each other, the prepreg for the multilayer has a higher content of the resin (containing an inorganic filler) relative to a glass fiber and high flowability, which increase the separation of resin/inorganic filler.